Pali Rohár <pali.rohar@xxxxxxxxx> writes: > What do you think what should kernel's exfat driver do in this case? > > To prevent such thing we need to use some kind of Unicode normalization > form here. > > CCing Gabriel as he was implementing some Unicode normalization for ext4 > driver and maybe should bring some light to new exfat driver too. We have an in-kernel implementation of the canonical decomposition normalization (NFD) in fs/unicode, which is what we use for f2fs and ext4. It is heated argument what is the best form for filesystem usage, and from what I researched, every proprietary filesystem does a different (and crazy in their unique way) thing. For exfat, even though the specification is quite liberal, I think the reasonable answer is to follow closely whatever behavior the Windows implementation has, whether it does normalization at all or not. Even if it is just an in-memory format used internally for lookups, assuming a different format or treating differently invalid file names can result in awkward results in a filesystem created on another operating system, like filename collisions or false misses in lookups. -- Gabriel Krisman Bertazi
